The invention relates to an electric-arc torch construction wherein a downstream flow of plasma gas through an annular gap between cathode and anode electrode elements is operative to transfer the arc in the downstream direction and external of the torch structure.
Existing torches of the character indicated are called upon to perform a variety of tasks, and if the torch is to have powder-spraying capability, as for metal or ceramic deposition upon a substrate or workpiece external to the torch, as many as four independent fluid flows may be required to serve a particular job. These independent flows may involve (a) a coolant liquid to be circulated through an external heat-exchanger, (b) a plasma-gas supply, (c) a powder supply involving fluidized powder in a carrier-gas flow, and (d) a shielding-gas flow to effectively isolate the region of arc discharge and powder transport between the torch and a workpiece. Existing torches to accommodate such independent flows are of complex mechanical construction, rendering unduly difficult the maintenance and/or repair of the torch.